The arctic fox is the only species of land mammal native to Iceland. Polar bears have also made their way to Iceland over the centuries. Other mammals found in the wild have been brought by humans, either deliberately (reindeer, mink) or inadvertently (mice and rats). Farm animals and pets may be released or escape into the wild but are not classified as wild animals.
The IINH conducted a major study on Iceland's wild reindeer population in connection with a planned dam project at Eyjabakkar. With the exception of this study, which took place from 1978 until 1983, the IINH has not employed experts to carry out research on land mammals. Research of this nature now takes place at other institutions in Iceland, namely:
- University of Iceland (arctic fox, field mouse)
- West-Iceland Institute of Natural History (mink)
- East-Iceland Institute of Natural History (reindeer)
Marine mammal fauna in the waters surrounding Iceland is richer and more diverse. Two seal species (grey seals and harbour seals) regularly pup in Iceland, while four other species of seal (Arctic ringed, harp, hooded and bearded seals) and walruses are occasional guests to Iceland.
A total of 23 dolphin and whale species have been spotted in Iceland's territorial waters. The IINH systematically collects information on whales sighted in the waters around Iceland. Research on whales and seals takes place at the Marine Research Institute.